Which of the following best summarizes the function of the respiratory system?

a. to transport oxygen to cells and wastes away from cells.

b. to protect the organs in the chest cavity
c. to move oxygen from the air into the body and carbon dioxide from the body into the air

d. to provide a barrier between the body and the environment
C** Which of the following is not true about the structure of an alveolus?

a. it has thick walls to trap gases that enter during breathing.

b. it has high surface area to allow lots of gas exchange.

c. it has a high concentration of oxygen and a low concentration of carbon dioxide.
A**